JPH0560498B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention has excellent transparency, impact resistance and rigidity,
The present invention relates to a block copolymer resin composition for sheets or films that provides molded products with good dispersibility and fewer flow marks. [Prior Art] Polymers mainly composed of styrenic hydrocarbons, especially sheets and films aimed at improving the impact resistance of so-called general-purpose polystyrene, are transparent when the content of vinyl aromatic hydrocarbons is relatively high, for example. Due to its excellent properties, its usage has been increasing in recent years, mainly in fields such as food packaging containers, daily necessities, and toys. Methods for producing such block copolymer resin compositions are disclosed in Japanese Patent Publication No. 19388-1988 and Japanese Patent Publication No. 47-1989.
-43618 Publication, Special Publication No. 51-27701, Special Publication Sho
Examples include Publication No. 52-32774 and Japanese Patent Publication No. 53-417. [Problems with the prior art] However, in the compositions of general-purpose polystyrene and vinyl aromatic hydrocarbon-conjugated diene block copolymers specifically disclosed in these methods, the compositions have a relatively low vinyl aromatic hydrocarbon content. Although the impact resistance of the product is improved, the transparency is inferior,
It also has the disadvantage of low rigidity. In addition, the above-mentioned composition having a relatively high vinyl aromatic hydrocarbon content has improved transparency and rigidity, but has flow marks due to poor impact resistance and poor dispersion of molded products.
This has caused a problem that significantly impairs the appearance of the molded product. Under these circumstances, the present inventors have conducted studies to obtain a molded product with excellent transparency, rigidity, and impact resistance, and fewer flow marks due to poor dispersion. The arrangement of the hydrogen polymer blocks and the molecular weight distribution of the vinyl aromatic hydrocarbon polymer blocks incorporated in the block copolymer are set within a certain range, and the content of vinyl aromatic hydrocarbons and the vinyl aromatic The inventors have discovered that the object can be achieved by mixing a block copolymer with an adjusted hydrocarbon blocking ratio and a styrene resin within a specific range, and have completed the present invention. [Means for solving the problem/structure of the invention] That is, the present invention has the following features: (a) The following general formula A-B-A or A-B-A-B-A (where A represents a vinyl aromatic hydrocarbon) The main polymer block, B, is a polymer block mainly composed of conjugated diene, and the block copolymer has a weight ratio of vinyl aromatic hydrocarbon and conjugated diene of 60/40 to 95/5. The ratio of the weight average molecular weight to the number average molecular weight of the vinyl aromatic hydrocarbon polymer block in the polymer is 1.2 to 2.0.
and (b) a block copolymer resin composition comprising 95 to 5% by weight of a styrene resin. In the block copolymer resin composition of the present invention, the block copolymer of the composition has the general formula A-B-A, A
As shown by -B-A-B-A, it is effective to have vinyl aromatic hydrocarbon polymer blocks at both ends of the polymer chain to improve the dispersibility and flow marks of molded articles of the composition. The block copolymer has a weight ratio of vinyl aromatic hydrocarbon to conjugated diene of 60/40 to 95/5, preferably 65/35 to 90/10. If the vinyl aromatic hydrocarbon content is less than 60% by weight, the composition will have poor transparency and rigidity, and if it exceeds 95% by weight, the composition will have poor impact resistance, which is not preferred. In the present invention, a polymer segment mainly composed of vinyl aromatic hydrocarbons is a polymer segment with a vinyl aromatic hydrocarbon content of 75% by weight or more, and a random combination of a conjugated diene and a vinyl aromatic hydrocarbon. It is composed of a polymer part and a vinyl aromatic hydrocarbon polymer part, or it is composed only of a vinyl aromatic hydrocarbon homopolymer part. In addition, a polymer segment mainly composed of conjugated diene is a polymer segment with a vinyl aromatic hydrocarbon content of less than 75% by weight, and a random copolymer portion of a conjugated diene and a vinyl aromatic hydrocarbon and/or Composed of a conjugated diene polymer portion. The vinyl aromatic hydrocarbons in the copolymer portion may be uniformly distributed or tapered. The block copolymer resin composition of the present invention has a weight average molecular weight (hereinafter referred to as "hereinafter referred to as") and a number average molecular weight (hereinafter referred to as "hereinafter referred to as")) of the vinyl aromatic hydrocarbon polymer block contained in the block copolymer of the composition.
The ratio is in the range of 1.2 to 2.0, preferably in the range of 1.3 to 1.8, more preferably in the range of 1.35 to 1.7.
If Mw/ is less than 1.2, the dart impact value will be poor, and if it exceeds 2.0, the compatibility will be poor. In order to obtain such a ratio between weight average molecular weight and number average molecular weight, the method for producing the vinyl aromatic hydrocarbon polymer portion is preferably a method in which vinyl aromatic hydrocarbon is continuously fed into the polymerization system and polymerized. Melt flow index (measured according to JISK-6870. Conditions are G condition and temperature
200°C, load 5 kg) is preferably 0.1 to 50 g/10 min, more preferably 0.5 to 35 g/10 min. /
If the Mn ratio is higher than 2.0, the stiffness of the composition decreases and the dispersibility of the molded product deteriorates, resulting in the problem of flow marks. Further, if the melt flow index is less than 0.1, the extrusion moldability is poor due to poor fluidity, and if it exceeds 50, the impact resistance of the composition is undesirable. Vinyl aromatic hydrocarbon polymer block/
Mn can be measured as follows. A vinyl aromatic hydrocarbon polymer component (LM
KOLTHOFF, et al., J. Polym.sci.1, 429
(1964)) using gel permeation chromatography (GPC), and using a conventional method (for example, the method described in "Gel Chromatography (Basic Edition)").
This refers to the value calculated according to the method described in the publication by Kodansha. The calibration curve for GPC is created using standard polystyrene commercially available for GPC. In the present invention, a particularly preferred block copolymer from the viewpoints of transparency, impact resistance, rigidity, and dispersibility of the block copolymer resin composition has a weight ratio of vinyl aromatic hydrocarbon to conjugated diene of 65/35. ~85/15,
Preferably it is 70/30 to 80/20. The block copolymer preferably has a vinyl aromatic hydrocarbon block rate of 50% by weight or more, more preferably 60% by weight or more. Blocking rate of vinyl aromatic hydrocarbon is 50% by weight
~80% by weight, preferably 60% to 80% by weight of the block copolymer improves the impact resistance of the composition in particular, and the block copolymer content of the vinyl aromatic hydrocarbon exceeds 80% by weight, preferably 85% to 80% by weight. The 95% by weight block copolymer gives the composition particularly good stiffness and dispersibility. Here, the block rate of vinyl aromatic hydrocarbon means that the amount of the vinyl aromatic hydrocarbon polymer component obtained by decomposing the block copolymer using the above-mentioned oxidative decomposition method is quantified, and that amount is calculated as the block copolymer component. The value (percentage) divided by the amount of vinyl aromatic hydrocarbons contained in the polymer. The weight ratio of the block copolymer and styrene resin in the block copolymer resin composition of the present invention is 95/5.
5/95, preferably 90/10 to 10/90. When the weight ratio of the block copolymer exceeds 95% by weight, the stiffness of the composition decreases. Furthermore, if the weight ratio of the block copolymer is less than 5% by weight, the impact resistance of the composition will decrease, which is not preferred. In the present invention, the styrenic resin is
A non-rubber modified styrenic polymer and/or a rubber modified styrenic polymer. The non-rubber modified styrenic polymer used in the present invention is obtained by polymerizing a vinyl aromatic hydrocarbon compound or a monomer copolymerizable therewith. Monomers copolymerizable with vinyl aromatic hydrocarbon compounds include α-methylstyrene,
Examples include acrylonitrile, ethyl acrylate, methacrylic ester, and maleic anhydride. Particularly preferred non-rubber modified styrenic polymers include polystyrene, styrene-α-methylstyrene copolymer, acrylonitrile-styrene copolymer, styrene-methacrylic acid ester copolymer, and styrene-maleic anhydride copolymer. These can be used alone or in a mixture of two or more. The rubber-modified styrenic polymer that can be used in the present invention is obtained by polymerizing a mixture of a vinyl aromatic hydrocarbon compound or a monomer copolymerizable therewith with an elastomer, and polymerization methods include suspension polymerization and emulsion polymerization. , bulk polymerization, bulk-suspension polymerization, etc. are generally carried out. Examples of monomers copolymerizable with the vinyl aromatic hydrocarbon compound include α-methylstyrene, acrylonitrile, ethyl acrylate, methacrylate, maleic anhydride, and the like. Examples of elastomers include natural rubber, synthetic isoprene rubber, butadiene rubber, styrene-butadiene rubber, high styrene rubber, polybutadiene rubber, chloroprene rubber, polybutene rubber, rubbery ethylene-propylene copolymer, and rubbery butadiene-acrylonitrile copolymer. Combined, butyl rubber, various nitrile rubbers,
Rubbery ethylene-vinyl acetate copolymers, rubbery ethylene-acrylic acid ester copolymers, rubbery atactic polypropylene resins, rubbery ethylene-acrylic acid ionomers, and the like are used. These elastomers are made of vinyl aromatic hydrocarbon compounds or monomers copolymerizable with them.
Generally, 2 to 70 parts by weight, more generally 3 to 50 parts by weight, per 100 parts by weight, are dissolved in the monomer or in the form of a latex and subjected to bulk polymerization, bulk-suspension polymerization, emulsion polymerization, etc. Particularly preferred rubber-modified styrenic polymers include impact-resistant rubber-modified styrene polymers, acrylonitrile-butadiene-styrene copolymers, acrylic ester-butadiene-styrene copolymers, and methacrylic ester-butadiene-styrene copolymers. , impact-resistant rubber-modified styrene-maleic anhydride copolymer, etc., and these can be used alone or in a mixture of two or more. The preferred amount of rubber-modified styrenic polymer mixed as styrenic resin is less than 30% by weight,
More preferably, it is less than 20% by weight. It is not preferable to mix more than 30% by weight because the transparency will decrease. The block copolymer of the block copolymer resin composition of the present invention is obtained by polymerization in a hydrocarbon solvent using an organolithium compound as an initiator. Hydrocarbon solvents include aliphatic hydrocarbons such as butane, pentane, hexane, isopentane, heptane, octane, isooctane; cyclopentane,
Alicyclic hydrocarbons such as methylcyclopentane, cyclohexane, methylcyclohexane, and ethylcyclohexane; or aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylene can be used. An organolithium compound is an organolithium compound in which one or more lithium atoms are bonded in the molecule, such as ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, tert-butyllithium, Examples include hexamethylene dilithium, butadienyl dilithium, and isoprenyl dilithium. In the present invention, vinyl aromatic hydrocarbons include styrene, o-methylstyrene, p-methylstyrene, p-tert-butylstyrene, 1,3-dimethylstyrene, α-methylstyrene, vinylnaphthalene, vinylanthracene, etc. However, styrene is a particularly common one.
These may be used not only alone, but also as a mixture of two or more. The conjugated diene is a diolefin having a pair of conjugated double bonds, such as 1,
3-butadiene, 2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-
Examples include butadiene, 1,3-pentadiene, 1,3-hexadiene, and particularly common ones include 1,3-butadiene and isoprene. These may be used not only alone, but also as a mixture of two or more. When producing the block copolymer of the block copolymer resin composition of the present invention, the method for adjusting the blocking rate of the vinyl aromatic hydrocarbon is as follows: (i) Using a mixture of the vinyl aromatic hydrocarbon and the conjugated diene; Methods such as continuously supplying the vinyl aromatic hydrocarbon and conjugated diene to the polymerization system and/or (ii) copolymerizing the vinyl aromatic hydrocarbon and conjugated diene using a polar compound or randomizing agent can be adopted. Polar compounds and randomizing agents include ethers such as tetrahydrofuran, diethylene glycol dimethyl ether, and diethylene glycol dibutyl ether, amines such as triethylamine and tetramethylethylenediamine, thioethers, phosphines, phosphoramides, alkylbenzene sulfonates, potassium and sodium Examples include alkoxides. Various additives can be added to the block copolymer of the block copolymer resin composition of the present invention depending on the purpose. Suitable additives include 30 parts by weight or less of coumaron-indene resins, terpene resins, softeners such as oils, and plasticizers. In addition, various stabilizers, pigments, anti-blocking agents,
Antistatic agents, lubricants, etc. can also be added. In addition, examples of antiblocking agents, lubricants, and antistatic agents include fatty acid amide, ethylene bisstearamide,
Sorbitan monostearate, saturated fatty acid esters of aliphatic alcohols, pentaerythritol fatty acid esters, etc. Also, as ultraviolet absorbers, p-
t-Butylphenyl salicylate, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3'-t-butyl-
5'-methylphenyl)-5-chlorobenzotriazole, 2,5-bis-[5'-t-butylbenzoxazolyl-(2)]thiophene, etc., "Practical Handbook of Additives for Plastics and Rubber" (Chemical Industry) Compounds listed in (Company) can be used. These are generally used in a range of 0.01 to 5% by weight, preferably 0.1 to 2% by weight. The composition of the present invention is obtained by mixing the block copolymer with a styrenic hydrocarbon polymer resin,
The mixing method may be any known method. For example, a method of mixing polymer solutions and removing the solvent to obtain a mixture, or a method using a roll,
A method of melt-mixing using an extruder or the like is used. [Effects of the Invention] The composition of the present invention has good transparency, excellent balance between impact resistance and rigidity, good dispersibility, and few flow marks in molded products, so it can be used as a molding material for various molded products. It can be used as That is, the composition of the present invention thus obtained can be made into extrusion molded products such as sheets and films by the same processing means as ordinary thermoplastic resins, either as is or after coloring. can. Furthermore, sheets and films made of the composition of the present invention can be used in a wide range of container and packaging materials fields, such as vacuum forming or pressure forming molded products as food containers and packaging, blister packaging materials, and as they are as packaging films for fruit and vegetable confectionery. Can be used. Furthermore, it can be used in applications where ordinary general-purpose resins are used, such as in the fields of toys, daily necessities, and miscellaneous goods produced by injection molding, blow molding, and the like. When a sheet or film made from the composition of the present invention is used for thermoforming, it has a shrinkage rate of 80° C. and is used at a shrinkage rate of less than 15% in both directions, preferably less than 5%. Some Examples are shown below, but these are intended to explain the present invention in more detail and are not intended to limit the scope of the present invention. Example 1 After internally purging the autoclave with nitrogen gas,
Prepare purified and dried cyclohexane 5,
Stirring and heating were performed, and when the temperature reached 70°C, 12 mmol of n-butyllithium was added. Next, 450 g of purified and dried styrene as A ₁ monomer was added at a constant rate over 60 minutes using a plunger pump, and then 80 g of purified styrene was added as B ₁ monomer.
Prepare a mixture of 250 g of dried butadiene,
This mixture was added at a constant rate with a plunger pump over 60 minutes. Next, 220 g of styrene as the _A2 monomer was polymerized at a constant rate over 30 minutes using a plunger pump, then 2 ml of methanol was added to stop the polymerization, and 10 g of 4-4 as an antioxidant was added.
Methyl-2,6-di-tert-butylphenol was added. The obtained block copolymer was pelletized using an extruder, and then 60% by weight of the block copolymer and 40% by weight of Styron 685 were mixed to obtain a sheet with a thickness of 0.7 mm using a sheet extruder. Furthermore, this sheet was vacuum formed to check the compatibility of polystyrene and block copolymer. As a result, a molded product was obtained that was transparent, had good gloss, had excellent dispersibility, and had good rigidity and impact resistance. Table 1 shows the physical properties of the obtained block copolymer resin composition. Comparative Example 1 After internally purging the autoclave with nitrogen gas,
Prepare purified and dried cyclohexane 5,
Styrene 335 purified and dried as A ₁ monomer
I prepared g. Next, 12 mmol of n-butyllithium and 1.5 g of tetrahydrofuran were added. The autoclave was heated to 70°C and stirring was continued for 60 minutes. Next, a mixture of 80 g of styrene and 250 g of purified and dried butadiene was prepared as a _B1 monomer, and this mixture was added at a constant rate over 60 minutes using a plunger pump, and polymerization was continued at 70°C. Next, 335 g of styrene was added as an _A2 monomer, and the polymerization was continued at 70°C for 60 minutes. Then, 2 ml of methanol was added to stop the polymerization, and 10 g of 4-methyl-2,
6-di-tert-butylphenol was added. Table 1 shows the physical properties of the resulting block copolymer composition measured in the same manner as in Example 1.

【table】

[Table] 〓 Examples 2 to 6 with separation The same equipment as in Example 1 was used, except that the monomer composition was changed and the amount of n-butyllithium (mmol) was changed to make MI a predetermined value. Polymerization was carried out in a similar manner. In addition, extrusion molding was carried out using the same procedure except that the amount of polystyrene mixed was changed. Table 2 shows the physical properties of the composition measured by the same method as in Example 1. It is clear that the block copolymer compositions within the scope of the present invention have excellent transparency, impact resistance, and compatibility. Comparative Examples 2 to 5 Using the same equipment as in Comparative Example 1, substantially the same operation was performed except that the monomer composition was changed and the amount of n-butyllithium (mmol) was changed to make MI a predetermined value. Polymerization was carried out. The same operation was also performed for extrusion molding. Table 2 shows the physical properties of the composition measured by the same method as in Example 1. It is clear that the balance of transparency, impact resistance, stiffness, and compatibility is poorer than that of compositions within the scope of the present invention.

【table】

【table】

Claims (1)

[Claims] 1 (a) The following general formula A-B-A or A-B-A-B-A (where A is a polymer block mainly composed of vinyl aromatic hydrocarbons, and B is a conjugated In a block copolymer in which the weight ratio of vinyl aromatic hydrocarbon and conjugated diene is 60/40 to 95/5, the weight ratio of the vinyl aromatic hydrocarbon in the block copolymer is 60/40 to 95/5. The ratio of the weight average molecular weight to the number average molecular weight of the combined block is 1.2 to 2.0) A block copolymer consisting of 5 to 95% by weight of a block copolymer represented by Resin composition.